Another "My bikes got a problem" Thread

[Squiggles]

plus EJ also needs a new rear tyre, the current one is both the wrong size and worn very square with no tread down the middle

yer, completely squared off aye?

Might pay to have that battery checked out, i reckon its had it (everyone seems to have charged it!)

[FROSTY:Me]

the silicone rubber bit was an attempt to secure the diaphram in place. it has been deformed before we got to it.--damb slide wasn't moving before and we had it moving--

[motorbyclist]

Bit of foam from para rubber will sort the air filter. Cheapa s chips

The diaphragm slide not moving will certainly mess up carburation(though usually would make it leaner, bu tit may not be going down - check that, it may be stuck in the UP position)

Sort the carb, and it'll be as good as new

it was stuck in the DOWN position. throttle was a butterfly behind the slide, assuming vaccuum - created when butterfly open and engine picks up - raises slide using the diaphragm, otherwise spring holds it down.

was thinking of playing around but choked the engine trying to get my finger in the gap to lift it

Go for the foam homemade replacement (or whichever is cheaper), unless he's riding metal roads it doesn't need to be hi tech, and I wouldn't use anything heavier in oil than a 2stroke mix to wet it (leave it dry even), then let the fuel dry off.

This all assumes that the carb settings are your only issue, I've found that when things start playing up people love to "Tune things up" and a rich mix with lot's of throttle/idle can hide all sorts of minor maintenance problems.

yeah i made clear to EJ that if a shop wanted more than $40 bucks for a filter, just buy some foam and we'll make 3 for $30. i've got some lube for my dirtbike and that works just fine, so we'll use a light app of that. would be good if he could get a paper pod filter; pocketbike one would be cheap and suitable.

and yeah, it always drives me nuts when people decide to fiddle with the idle/fuel mix before doing the basic stuff like checking the carb is actually working normally. then they don't count the number of turns, nor know exactly what the engine was doing before they fiddled with it!

Might pay to have that battery checked out, i reckon its had it (everyone seems to have charged it!)

probably due to all the starting with no running. will use the big truck battery for now till it's fixed

the silicone rubber bit was an attempt to secure the diaphram in place. it has been deformed before we got to it.--damb slide wasn't moving before and we had it moving--

you mean it was physically jammed or just not moving when it should?

(myself only learnt about silicone and carby's using it to seal up a bowl. a lump dissolved off and blocked the jet)

[FROSTY:Me]

Ok -the jetting hasnt been touched. Nor have any screws on the carb.
Whats been done is the petroil mixture drained and the crankcase ventilated
The airbox got dried out
I screwwed the plug in tight and used my jet pack.The bike started and idled on choke. Wont rev up though
The carb was hauled out and the jets checked for blockage.
The damb slide seemed to be jammed but then it freed up and seemed to be going up and down propperly.
I hauled the lid off the carb and the diaphram wasnt attatched propperly -as in it wasn't in the groove as it should be. something in that carb is definitely sctrewey

My thinking is - Ok YOUR FXr runs fine. You swapped CDI units and no effect.
The carb comes out in a couple of secs so try swapping the carb over and see if the bike runs propperly on your carb.
I don't doubt that the blocked filter is making a difference b ut the bike should rev up and run okish with the filter out.

[motorbyclist]

Ok -the jetting hasnt been touched. Nor have any screws on the carb.
Whats been done is the petroil mixture drained and the crankcase ventilated
The airbox got dried out
I screwwed the plug in tight and used my jet pack.The bike started and idled on choke. Wont rev up though
The carb was hauled out and the jets checked for blockage.
The damb slide seemed to be jammed but then it freed up and seemed to be going up and down propperly.
I hauled the lid off the carb and the diaphram wasnt attatched propperly -as in it wasn't in the groove as it should be. something in that carb is definitely sctrewey

My thinking is - Ok YOUR FXr runs fine. You swapped CDI units and no effect.
The carb comes out in a couple of secs so try swapping the carb over and see if the bike runs propperly on your carb.
I don't doubt that the blocked filter is making a difference b ut the bike should rev up and run okish with the filter out.

sweet, thanks for the history, and my thoughts exactly if the diaphragm doesn't come right.

and of course the filter doesn't help, but will want one in there when we finally get it going and get the mix right. we of course don't know if the previous owner fiddled with the carb at all nor how much.

reckon it's still got the original, ie correct, size jet/needle in there?

[FROSTY:Me]

Thing is the bike HAS run fine for EL. So logic says as long as nowts been fiddled with it should run.
The main issue has been identified so by swappping the carb over even without the filter the bike starting and revving up will decide definitely that the issue is the carb

[motorbyclist]

ah, logic, of course.... now why didn't i consider that? - i never assume the previous owner hasn't rooted the bike and "fixed" it soley to sell it on to the next unsuspecting trademe user unless i know the seller personally.


i think it's a safe bet that it's the carb - running very rich and obviously not operating. will of course swap carbs at some point to be sure that's the only issue at hand.

any info on what the oily petrol did to the cams? valve stem seals? (there isn't any blue smoke - yet)

[gijoe1313]

You good thing you, working into the wee hours of the night! Was good to meet you and your family yesterday! Cheers to Frosty for the lend of some better tie-downs, I rushed back to drop them off, but was only confronted with the slow steady tick of the electric fence!

[EJK]

Thanks everyone last night.

Sort the carb, and it'll be as good as new

I hope so lol

[Squiggles]

time for a gn carb i say

[EJK]

time for a gn carb i say

I know, but GIJUSTIN1313 says "Diaphram can be fixed! "



GN carb = Last resort

[FilthyLuka]

GN carb = Last resort

If you can find one on trademe for like $20 i dont see why you couldn't just do that... would go a bit better too. I can give you dimensions for pods and what not, so the entire airbox can go. Meaning also if the tank gets busted again, no chance of the same thing happenin

Hell, you could probably even grab the carb of this:

http://www.trademe.co.nz/Trade-Me-Mo...36223.htm?p=27

[EJK]

What was about the carb tuning? timing tuning? something like that?

Whats that?

P.S. Bike still won't start easily when the engine is cold. Is there a way that I can fix this?

[xwhatsit]

Kick harder?

If you're going to do a carb swap, get one of my CB250RS carbs. Round-slide pumper MX-style. Instant *SNAP*. That thing would scream.

I wouldn't be worrying about cold-starting right now until the carb is actually back together. Might be something as simple as pilot screw set right.

[motorbyclist]

If you can find one on trademe for like $20 i dont see why you couldn't just do that... would go a bit better too. I can give you dimensions for pods and what not, so the entire airbox can go. Meaning also if the tank gets busted again, no chance of the same thing happenin

Hell, you could probably even grab the carb of this:

http://www.trademe.co.nz/Trade-Me-Mo...36223.htm?p=27

haha yeah, his up squiggles for discount parts

i did suggest that EJ look at a GN or DR carb and/or pod filter.

What was about the carb tuning? timing tuning? something like that?

Whats that?

P.S. Bike still won't start easily when the engine is cold. Is there a way that I can fix this?

"tuning" is just the term for "optimising" the engine, if you like.

to burn correctly you need a certain ratio of fuel to air entering the engine:
too much fuel (rich) and it doesn't all burn properly, fouling up the engine and plug with carbon and not giving much power.
too little fuel (lean) and it creates far too much heat and things either melt or expand too much and seize up. EDIT: even less fuel and the thing won't have enough to run on!

also, to acheive maximum efficiency the engine should be running as hot as physically possible. unfortunately modern materials mean that our highest running temperatures are only a fraction of what the petrol fuel can manage - too hot (over 900 degrees) and things get soft, melt and/or expand too far. this also means that when you go to start a cold motor, it doesn't produce much power at all and thus is hard to keep running - PLUS the engine hasn't expanded yet to there isn't very good seals where needed PLUS the oil is both thick and all sitting in the sump. the choke is used to alter the fuel mix to again make the engine run well at low temperatures, and even then you may have trouble due to thick oil, high friction where oil is yet to reach, poor tolerances etc etc. cold starting problems are normal. you may hear around KB or people blocking off two stroke radiators to get more power - same story again with the added challenge of burning off oil. diesel (compression ignition) engines are MUCH more efficient than petrol engines for these reasons, using pressure and temperature to ignite the fuel rather than a spark gives upwards of 60% efficiency, much more than the 35% ideal efficiency of the 4 stroke igntion engine

i can get into the chemistry and thermodynamics of it if you like

getting the right fuel mix is acheived by tuning the carb. the whole engine can be further tuned to run smoother/better by adjusting spark and valve timing, and when we're finished with the FuXR we'll include turbo boost, backpressure, high compression pistons, increasing the displacement, etc, then throw on a slipper clutch and carbon fibre bodywork

timing is generally the spark timing. the fuel takes time to burn, so it pays to fire just a bit before top dead centre (TDC) and the expansion of the burning fuel actually gives even higher compression to the unburnt gases - higher compression means more efficiency and MOAR POWER. but of course it does press back on the piston slightly among a few other trade-offs. as such there is an optimum spark time for a given engine at a given rpm. ideally we vary it so it's always at optimum, but asfaik the fxr isn't capable of that so we're stuck with a given time that we can set.

timing can also include valve timing. both exhaust and inlet valves open slightly before you would expect them to, and close again a fair bit later than you would think they would too. this is due to the time required to open/close them, and the inertia/momentum/elasticity/velocity of the various gases in the engine/intake/exhaust. again it's a bit of a trade off as there is an optimum setting for a certain rpm that won't work well elsewhere. gotta get as much fuel in as possible, as much compression as possible, and the least trouble removing the waste gases as possible

it's these tradeoffs that typically give an engine it's "power band", that kick the fxr gives at 8000rpm through to redline is when it starts to run at it's best efficiency. two strokes have such 'aggressive' bands as due to the nature of them they are tuned to only work efficiently at high revs. as such a power valve helps fix this and widen the power band, giving smoother power.

advances in electronic controls have given us technologies that overcome these problems. fuel injection to give the perfect mix, variable valve and spark timing to give the optimum running conditions at all engine speeds. it's getting to the point now where they can do away with cams and associated moving parts with electronically controlled hydraulics pushing the valves!

so enjoy this age of carburetors and cam chains while it lasts, manually and mechanically setting things the way you see best with screwdrivers and hammers. already today, in order to tune many modern bikes and cars all one has to do is plug in their laptop, and that's only if the on board computers aren't quite getting the job right automatically. come the shift towards electric vehicles there won't even be anything to tune without physically altering the already 99% efficient layout of the motor's windings - that 1% loss is basically a slight heat loss and friction via cooling fans and bearings!


and that just about covers everything


i am so sussed for the MECHENG223 "machines and mechanisms" test next week